Postoperative Changes of Spinopelvic Sagittal Parameters After Cervical Laminoplasty for Cervical Spondylotic Myelopathy.

STUDY DESIGN: A retrospective analysis of prospectively collected data. OBJECTIVE: To investigate postoperative changes of spinopelvic sagittal parameters after laminoplasty for cervical spondylotic myelopathy (CSM) accompanying postoperative cervical kyphotic deformity or cervical regional sagittal imbalance. SUMMARY OF BACKGROUND DATA: To the best of our knowledge, no study has been reported concerning postoperative changes of spinopelvic sagittal parameters accompanying postoperative deterioration of cervical sagittal alignment or balance after cervical laminoplasty. METHODS: Forty-five CSM patients without preoperative cervical kyphosis who underwent laminoplasty were included. None of the 45 patients had a medical history of previous spine surgery, hip joint surgery, or knee joint surgery. The patients were divided into 2 groups (kyphosis and lordosis groups) according to postoperative C2-7 angle, and they were also divided into 2 other groups (imbalance and balance groups) according to postoperative C1-7 sagittal vertical axis. Postoperative changes (Δ) of T1 slope (T1S), thoracic kyphosis, thoracolumbar kyphosis (TLK), lumbar lordosis (LL), Pelvic tilt, and C7 sagittal vertical axis were measured comparing lateral radiographs of the whole spine in the standing position taken at 1 year postoperatively with those before surgery. RESULTS: Both T1S and TLK significantly decreased after cervical laminoplasty in the kyphosis group compared with the lordosis group. On the other hand, both T1S and TLK increased significantly, and LL significantly decreased after surgery in the imbalance group compared with the balance group. CONCLUSIONS: At 1 year after laminoplasty for CSM, both T1S and TLK significantly decreased accompanying postoperative cervical kyphotic deformity as a compensatory action for postoperative cervical kyphosis to maintain the global sagittal balance of the spine, whereas both T1S and TLK increased significantly, and LL significantly decreased accompanying postoperative cervical reginal sagittal imbalance which resulted in postoperative forward inclination of the whole spine.

Assessment of effects of rhBMP-2 on interbody fusion with a novel rat model.

BACKGROUND CONTEXT: The effects of using off-label recombinant human bone morphogenetic protein (rhBMP)-2 for interbody fusion are controversial. Although animal models of posterolateral fusion are well-established, establishing animal models to validate the safety and efficacy of interbody fusion is difficult, which may contribute to the inconsistent clinical results. PURPOSE: To develop a novel animal model of interbody fusion in rat coccygeal vertebrae without destroying bony endplates. STUDY DESIGN: An experimental animal study. METHODS: Forty-five male Sprague-Dawley rats underwent coccygeal interbody fusion without violating vertebral endplates. The animals were divided into three different groups based on the materials that were implanted into the interbody space (1) allogeneic iliac bone (IB) alone (IB group), (2) IB and 3 µg of rhBMP-2 (BMP low-dose group), or (3) IB and 10 µg of rhBMP-2 (BMP high-dose group). Fusion rates were investigated using microcomputed tomography 6 weeks after the operation. The incidence of adverse events, including soft-tissue swelling, delayed wound healing, osteolysis, and ectopic bone formation were evaluated. The total number of adverse events (using the adverse event score) in each group and the swelling ratio (calculated using the surgical site tissue volume [TV; TV on postoperative day 1/preoperative TV]) were also evaluated. RESULTS: The fusion rates in the BMP low- and high-dose groups (33.3% and 46.7%) were not significantly different, but both were significantly higher than that in the IB group (0%) (p=.042 and .006, respectively). Significant differences in the incidence of osteolysis, adverse event scores, and swelling ratios were observed only between the BMP high-dose and IB groups (p=.043, .006 and .014, respectively). CONCLUSIONS: We developed a novel rat model of interbody fusion in which the vertebral endplates were not violated, reflecting the normal clinical setting. rhBMP-2 use increased the fusion rate, but a higher dose of rhBMP-2 did not lead to a higher fusion rate than that for low-dose rhBMP-2; conversely, it led to an increase in the occurrence of adverse events. CLINICAL SIGNIFICANCE: This novel rat model of coccygeal interbody fusion that preserved bony endplates has clinical significance for validating the effectiveness of biologics or bone graft substitutes before clinical trial.

Development of scoliosis in young children with osteogenesis imperfecta undergoing intravenous bisphosphonate therapy.

The purpose of this study was to clarify the prevalence of scoliosis and determine risk factors for the development of scoliosis in young children with osteogenesis imperfecta (OI) who underwent intravenous pamidronate (PAM) therapy. Thirty-four young children with OI who had no scoliosis at the first PAM administration underwent cyclic PAM therapy alone. The medical records and radiographs of these patients were retrospectively reviewed. We examined the relationship between scoliosis (Cobb angle ≥ 10) and type of OI (Sillence classification: types I, III, and IV), physical mobility, Z-scores of bone mineral density in L2-4 of the lumbar spine (L2-4 BMD Z-scores), age of patients at first treatment with PAM, pelvic frontal tilt and leg-length discrepancy. The prevalence of scoliosis was 23.5% in 34 young children with OI who underwent PAM therapy for a mean of 4.2 years. Lower L2-4 BMD Z-scores, the presence of coronal and sagittal vertebral deformities and higher percentage of corrective osteotomy in the lower extremities were significant risk factors for the development of scoliosis. In patients with type III or IV OI, L2-4 BMD Z-scores were significantly lower (p = 0.02) and the percentage of patients who started PAM therapy in early childhood was significantly lower in scoliosis group than in the non-scoliosis group (p = 0.01). Development of scoliosis depends on the severity of OI and has a strong relationship with bone fragility even under PAM therapy. Starting intravenous PAM therapy in infancy or early childhood has a potential to prevent the occurrence and progression of scoliosis associated with bone fragility in young children with severe type III or IV OI.

BMP-2/7 heterodimer strongly induces bone regeneration in the absence of increased soft tissue inflammation.

BACKGROUND CONTEXT: Bone morphogenetic protein (BMP)-2/7 heterodimer is a stronger inducer of bone regeneration than individual homodimers. However, clinical application of its potent bone induction ability may be hampered if its use is accompanied by excessive inflammatory reactions. PURPOSE: We sought to quantitatively evaluate bone induction and inflammatory reactions by BMP heterodimer and corresponding BMP homodimers using ultra-high resolution magnetic resonance imaging (MRI) and micro-computed tomography. STUDY DESIGN: An experimental animal study was carried out. METHODS: A total of 32 absorbable collagen sponge implantations into dorsal muscle were performed in rats of four different groups (control group, 0 µg BMP; recombinant human (rh)BMP-7 group, 3 µg rhBMP-7; rhBMP-2 group, 3 µg rhBMP-2; rhBMP-2/7 group, 3 µg rhBMP-2/7). Inflammatory reactions were evaluated by 11.7-T MRI (axial T2-weighted imaging using rapid acquisition with relaxation enhancement) at postoperative days 2 and 7. Bone volumes (BVs) of the induced ectopic bone were quantified at postoperative day 7. In addition, immunohistochemical staining for interleukin (IL)-1ß, IL-6, and tumor necrosis factor (TNF)-α was performed in samples obtained on postoperative day 2. Bone formation (BF)-to-inflammation (IM) ratios were calculated by dividing BVs by values of inflamed areas. RESULTS: At postoperative day 2, the mean volume of T2 high area on MRI scans in BMP-2 group was significantly larger than that in control group. In contrast, the BMP-2/7 had no difference in the mean volume of T2 high area compared with the control group; however, there was no difference between the BMP-2/7 compared with BMP-2 group. At postoperative day 7, the volumes of T2 high area were not different between the groups. Mean BV of the newly formed bone on postoperative day 7 was significantly greater in BMP-2/7 group than in BMP-7 groups. No new bone formation was observed in control group. BF-to-IM ratio in BMP-2/7 group was significantly higher than those in BMP-2 and BMP-7 homodimer groups. Immunohistochemistry experiments did not reveal differences in expression levels of IL-1ß, IL-6, or TNF-α in samples from BMP-2, BMP-7, and BMP-2/7 groups. CONCLUSIONS: This study demonstrated that BMP-2/7 heterodimer has stronger bone induction ability without accompanying increased inflammatory reactions (the increased BF-to-IM ratio) than those observed by BMP-2 or BMP-7 homodimers. These results suggest that BMP-2/7 heterodimer can be an alternative to BMP-2 and BMP-7 homodimers in clinical applications, although further translational studies, including whether lower doses of BMP heterodimer may produce similar bone formation compared with the BMP homodimers but produce a reduced inflammatory response, are required.

ONO-1301 Enhances in vitro Osteoblast Differentiation and in vivo Bone Formation Induced by Bone Morphogenetic Protein.

STUDY DESIGN: In vitro and in vivo assessment of osteogenic effect by prostacyclin agonist (ONO-1301). OBJECTIVE: The aim of this study was to investigate the effects of ONO-1301 on in vitro osteoblastic differentiation and in vivo bone formation induced by bone morphogenetic protein (BMP). SUMMARY OF BACKGROUND DATA: Among prostaglandins (PGs), PGE2 is the most abundant in bone tissue and its effects on bone formation have been well studied. PGI2 (prostacyclin) is the second most abundant PG in bone tissue and plays important roles in hemodynamics. However, the effects of PGI2 on osteoblast differentiation and bone regeneration have not been elucidated. METHODS: The effects of PGI2 agonist (ONO-1301), with and without recombinant human (rh) BMP-2, on osteoblastic differentiation and cell proliferation were investigated in vitro using alkaline phosphatase (ALP) and WST-1 assays. Murine primary osteoblasts and cell lines (ST2, MC3T3-E1, C2C12, and CH310T1/2) were used for the study. The effects of ONO-1301 on rhBMP-2 induced bone formation were investigated in a mouse model of muscle pouch transplantation (ectopic model) and in a rat model of spinal fusion (orthotopic model). RESULTS: ONO-1301 significantly increased ALP activity in the primary osteoblasts and ST2 cells. In addition, cotreatment with ONO-1301 and rhBMP-2 significantly increased ALP activity in the primary osteoblasts, as well as in ST2 and MC3T3-E1 cells. Cell proliferation was not affected by both ONO-1301 and ONO-1301 as well as rhBMP-2. In the ectopic model, ONO-1301 significantly increased the volume of ectopic bone whose formation was induced by BMP. In addition, in the orthotopic model, ONO-1301 significantly increased bone volume and fusion rate. CONCLUSION: This study has demonstrated that the PG IP agonist ONO-1301 improves in vitro BMP-2 induced osteoblast differentiation and in vivo ectopic and orthotopic bone formation. The results suggest that ONO-1301 has a potential clinical application as an enhancer of BMP-induced bone formation. LEVEL OF EVIDENCE: N/A.

Modeling and remodeling effects of intermittent administration of teriparatide (parathyroid hormone 1-34) on bone morphogenetic protein-induced bone in a rat spinal fusion model.

BACKGROUND: Bone morphogenetic protein (BMP)-based tissue engineering has focused on inducing new bone efficiently. However, modeling and remodeling of BMP-induced bone have rarely been discussed. Teriparatide (parathyroid hormone [PTH] 1-34) administration initially increases markers of bone formation, followed by an increase in bone resorption markers. This unique activity would be expected to accelerate the modeling and remodeling of new BMP-induced bone. METHODS: Male Sprague-Dawley rats underwent posterolateral spinal fusion surgery and implantation of collagen sponge containing either 50 µg recombinant human (rh)BMP-2 or saline. PTH 1-34 (60 µg/kg, 3 times/week) or saline injections were continued from preoperative week 2 week to postoperative week 12. The volume and quality of newly formed bone were monitored by in vivo micro-computed tomography and analyses of bone histomorphometry and serum bone metabolism markers were conducted at postoperative week 12. RESULTS: Microstructural indices of the newly formed bone were significantly improved by PTH 1-34 administration, which significantly decreased the tissue volumes of the fusion mass at postoperative week 12 compared to that at postoperative week 2. Bone histomorphometry and serum analyses showed that PTH administration significantly increased both bone formation and resorption markers. Analysis of the histomorphometry of cortical bone identified predominant periosteal bone resorption and endosteal bone formation. CONCLUSIONS: Long-term intermittent administration of PTH 1-34 significantly accelerated the modeling and remodeling of new BMP-induced bone. CLINICAL RELEVANCE: Our results suggest that the combined administration of rhBMP-2 and PTH 1-34 facilitates qualitative and quantitative improvements in bone regeneration, by accelerating bone modeling and remodeling.